Wireless access systems have been widely deployed to provide various types of communication services such as voice or data. In general, a wireless access system is a multiple access system that supports communication of multiple users by sharing available system resources (a bandwidth, transmission power, etc.) among them. For example, multiple access systems include a Code Division Multiple Access (CDMA) system, a Frequency Division Multiple Access (FDMA) system, a Time Division Multiple Access (TDMA) system, an Orthogonal Frequency Division Multiple Access (OFDMA) system, and a Single Carrier Frequency Division Multiple Access (SC-FDMA) system.
Recently, the structure of a radio access system has changed to a structure in which small cells (e.g., pico cells, femto cells, etc.) having various shapes and small sizes are connected to a macro cell having a relatively large size. This aims to enable a user equipment (UE), which is an end user, to receive a high data rate to increase quality of experience in a state in which multilayered cells having vertical layers, in which conventional macro cells are fundamentally involved, are mixed.
According to one of the current 3rd Generation Partnership Project (3GPP) standardization categories, Small Cell Enhancements for E-UTRA and E-UTRAN SI; e.g., RP-122033, enhancement of indoor/outdoor scenarios using low-power nodes is discussed under the title of small cell enhancement. In addition, scenarios and requirements for the small cell enhancement are described in 3GPP TR 36.932.
Considering the development trend, a larger number of smaller cells will be deployed within macro cells and thus final UEs will be located physically nearer to a network. Accordingly, it is expected that communication will be conducted through UE-based zones in a future-generation wireless access network, instead of conventional physical cell-based communication. To realize communication through UE-based zones with the aim of increasing throughput, technical issues should be handled to provide a service providing unit such as a UE zone, different from a conventional service providing unit such as a physical cell. The emergence of these small cells may significantly affect a current Remote Area Network (RAN).
Furthermore, the 5G system which is a future wireless communication system considers environments in which a lot of small cells are deployed. In such environments, handover among a remarkably large number of cells according to UE mobility is expected, compared to a macro eNB environment of LTE/LTE-A. Accordingly, interception of a UE identifier may be easier and thus protection of location information of a UE becomes increasingly important.